BREWSTER: BIRDS OF THE CAPE REGION, LOWER CALIFORNIA. 17 
& 
taken at Monterey, California, in the winter of 1896-97 by Mr. Alvin Seale, I 
have become convinced that the doubts which certain writers have expressed 1 
concerning the specific distinctness of hypolewcus and craveri are without foun- 
dation. The chief characters which appear to distinguish the two birds are as 
follows : — 
B. hypoleucus. Upper parts blackish slate often with a decided tinge of bluish ashy ; 
lining of wings clear, immaculate white; inner webs of outer primaries nearly 
or quite pure white to within a short distance from the tips; many of the dark 
(bluish slate) colored feathers on sides of body conspicuously tipped with white. 
B. craveri. Upper parts seal brown; lining of wings smoky gray or grayish white, 
many of the feathers with conspicuous spots or blotches of faded ashy brown; 
inner webs of all the primaries plain brown only a shade or two lighter than 
that of the outer webs and never approaching white save at the extreme bases 
of the feathers, which are sometimes brownish white; dark colored feathers on 
sides of body without light tipping. 
The clear slaty tone of the upper parts in my examples of hypoleucus may 
be due to the fact that the birds were all taken at somewhat earlier dates in 
the winter than any of my specimens of craveri, but the other characters above 
mentioned are obviously not of a kind likely to be materially affected by mere 
seasonal differences of plumage. 
The dissimilarity in respect to the color of the wing lining has been long 
known, only its constancy as well as its significance having been questioned. 
In the specimens before me it is absolutely constant, at least within certain 
limits. Most of my specimens of cravert have the under coverts conspicuously 
blotched and spotted with slaty or brownish on a smoky or ashy white ground, 
but in a few birds the lining of the wing is pure white and, at first glance, 
apparently almost immaculate. On close inspection, however, I find that 
aJl such specimens in my series have the white or whitish on most of the 
under wing coverts confined to the tips and edges of the feathers, their central 
portions being either slaty or brown. When the plumage is disarranged these 
dark markings become at once conspicuous. 
The coloring of the wing lining varies greatly in young birds. The natal 
down which, at first, completely clothes the under surface of the wings is 
apparently always uniformly dark (reddish brown). Among the birds which 
have shed this down some have the under wing coverts dark slate or slaty 
brown relieved by only a few whitish markings on the tips of the feathers. 
With others of apparently similar age the under surtace of the wings is not 
darker than in most of the adults. Asa rule, however, the ground color of 
the under coverts appears to become lighter as the bird grows older, but the 
brown on the centers of the feathers evidently persists through life. 
1 Dr T. H. Streets and Mr. W. R. Ogilvie-Grant have suggested that craveri 
may be merely Aypoleucus in full breeding plumage, while Mr. Anthony has “thought 
it possible that it may prove to be a plumage of the young carried through one or 
more moults.” 
VOL. XLI. — No. 1 2 
